Race Driver GRID
I tested this absolutely gorgeous-looking game with FRAPS, as well, and in order to keep things simple, I decided to capture frame rates over a single, longer session as I raced around the track. This approach has the advantage of letting me report second-by-second frame-rate results.

Yowza. The Radeon HD 4870 is nearly twice as fast as the 3870, which is good enough to put it at the very top of the single-GPU solutions. Two 4850 or 4870 cards seem to scale well in CrossFire, as well.

For what it's worth, I tried re-testing the 3870 X2 with the new Catalyst 8.6 drivers to see whether they had a CrossFire profile for GRID, like the 4800 series drivers obviously do, but performance was the same. I also tried renaming the game executable, but that attempt seemed to run afoul of the game's copy protection somehow. Oh well.